The group has already confirmed that the Euro 5 engine is at the centre of investigations into its manipulation of US emissions tests – Euro 6 engines aren’t affected.

The 4,000 vehicles affected by the move are from Audi, SEAT, Skoda, Volkswagen, and represent around 3% of the group’s total UK stock. The vehicles were still on sale past the 1 September deadline for the introduction of Euro 6 standards as carmakers were permitted to clear stocks of Euro 5 vehicles.

According to reports, the vehicles will be put back on sale once modified. Customers who have placed an order for an affected vehicle have also been given the option to pull out of the sale without penalty or still take delivery of the vehicles before or after the modifications have been made.

Meanwhile the RAC Foundation has compared the numbers of vehicles affected by the software issue that have already been released by VW alongside DVLA licensing data and calculated that in the UK, 45% of all Audi diesel cars on the road, 37% of all VW and SEAT diesel cars, and 25% of all Skoda diesel cars are affected.

It has also been announced that the EPA in the US will extend its diesel probe into other carmakers' vehicles.